Question

Find the sum of the first 7 terms of the series. 6-12+24-48+...

Answer 1

Answer: C is correct 258 i just took the test

Explanation:

Answer 2

Answer: 258

Explanation:

Since, the sum of GP is,

`S_(n)=(a(r^n-1))/(r-1)`

where r is the common ratio,

a is the first term,

n is the number of term,

Here, series is, 6, -12, 24, -48, _ _ _ _

Which is a GP ( Because there is common ratio in the given consecutive terms )

So, for the above series, a = 6, r =
`(6)/(-12)=-2` and n = 7,

⇒
`S_(7)=(6(-2^7-1))/(-2-1)`

⇒
`S_(7)=(6(-128-1))/(-3)`

⇒
`S_(7)=(6(-129))/(-3)`

⇒
`S_(7)=(774)/(3)=258`

Thus, the sum of the 7 terms of the given series is 258.